polynomials with Big-Oh

[bioin...@gmail.com]

Given a Polynomial with an asymptotic term:

>>> from sympy import series, poly

>>> from sympy.abc import x

>>> p=poly(series(1/(1-x),n=3))

>>> p

Poly(x**2 + x + O(x**3) + 1, x, O(x**3), domain='ZZ')

how do I remove the O(x**3) term so that I can use methods like p.all_coeffs()?

Thanks in advance,

-Kevin

[bioin...@gmail.com]

On Sunday, March 8, 2015 at 7:02:20 PM UTC-4, Mihir Wadwekar wrote:

You can try something like this, though I am not sure if it's the best way to do it.

>>> Poly( p.as_expr().removeO() , domain = 'ZZ' )

That is one of the first things I tried, but not after converting to an expression.  Is it a bug that p.removeO() doesn't work on Poly instances?

Thanks!

-Kevin

 

[Aaron Meurer]

Remove the O when calling the series before you create the Poly, like
poly(series(1/(1-x),n=3).removeO()).

Aaron Meurer

On Sun, Mar 8, 2015 at 11:19 PM, Mihir Wadwekar <m.mi...@gmail.com> wrote:
> It's not a bug. It's not been defined for polynomials. Asymptotic notations
> are associated with series which are currently treated as expressions.
> Perhaps someone else can provide a better explanation.
>
> btw, for your particular case, this would be better:
>
>>>> z = series(1/(1-x),n=3).removeO() # series returns an expression
>>>> p = Poly(z, domain = 'ZZ' )

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